Abstract

A novel type of integrated refractive-diffractive varifocal membrane lens is designed and analyzed by wave-optical methods. In contrast to other hybrid devices, the diffractive microstructure is directly imprinted onto the soft deflecting membrane, allowing for a high level of integration. Elastic deformation is taken into account by mechanical simulations with the finite element method (FEM). We show, that the superimposed structure can considerably suppress chromatic and spherical aberration. Furthermore, our algorithm is successfully applied to design a confocal hyperspectral lens.

(a) Geometric representation of the Huygens-Fresnel method used. (b) Comparison of the Huygens-Fresnel-method with 3D Gaussian beam calculations. The intensity distribution on the optical axis results from a 4th order asphere lens at z = 0 with plane wave illumination.

(a) Comparison of the designed DOE with the distorted and radially elongated structure after membrane deflection. (b) Normalized intensities along the optical axis for three different membrane pressures at a wavelength of 535 nm for both cases, compared with a purely refractive unstructured membrane.

Focal shift as a function of wavelength λ, relative to the focal length at λ = 535 nm and diffraction efficiency as a function of wavelength for the achromatic case. Since the DOE introduces an offset in focal length, the absolute focal length of the purely refractive lens is slightly higher at the same pressure.

(a) Irradiance distribution on the optical axis for different wavelengths (420 nm – 650 nm) and a membrane pressure of −0.5 kPa. (b) Schematic of the investigated setup. (c) Transmission spectra of the system as a function of lens pressure.